Dar·da·nelles or Hel·les·pont\ˈhe-lə-ˌspänt\ or ancient Hel·les·pon·tus\ˌhe-lə-ˈspän-təs\
Narrow strait between the peninsula of Gallipoli in Europe and the mainland of Turkey in Asia. Some 38 mi (61 km) long and 0.75–4 mi (1–6 km) wide, it links the Aegean Sea with the Sea of Marmara. Strategically important from antiquity, the Dardanelles was defended by Troy from its position on the Asian side. In 480 BC the Persian Xerxes I crossed the strait to invade Greece; Alexander the Great also crossed it in 334 BC on his expedition against Persia. Held by the Roman Republic and Empire and the Byzantine Empire and later by the Ottoman Empire, it is of great strategic and economic importance as the gateway from the Black Sea to Istanbul and the Mediterranean Sea.